1. Field of the Invention
The invention pertains to a chemical mechanical abrasive composition. The chemical mechanical abrasive composition is useful in polishing the surface of a semiconductor wafer.
2. Description of the Prior Art
Chemical mechanical polishing (CMP) is a planarization technique which was developed to address the problem associated with the difficulty in focus during a photolithography process for producing integrated circuits owing to the difference in the height of deposited films. Chemical mechanical polishing technique was first applied to the production of the elements with a size in the order of 0.5 microns. With the reduction in the size of elements, the chemical mechanical polishing technique was applicable to an increased number of layers. Until the elements were developed to the order of 0.25 microns, the chemical mechanical polishing became a main and essential planarization technique. In general, the polishing method for producing a wire circuit comprises mounting a semiconductor wafer on a spinning platen equipped with an abrasive head and applying an abrasive slurry comprising abrasive particles and an oxidant to the surface of the wafer to enhance the abrasion efficacy.
U.S. Pat. No. 5,225,034 discloses a chemical mechanical abrasive slurry which comprises AgNO.sub.3, solid abrasive particles, and an oxidant selected from H.sub.2 O.sub.2, HOC1, KOC1, KMgO.sub.4, or CH.sub.3 COOOH. The slurry is used for polishing a copper layer on a semiconductor wafer so as to produce a copper wire on the wafer.
U.S. Pat. No. 5,209,816 discloses a method for polishing an Al-- or Ti-- containing metal layer with a chemical mechanical abrasive slurry. The abrasive slurry contains, in addition to a solid abrasive material, about 0.1-20% by volume of H.sub.3 PO.sub.4 and about 1-30% by volume of H.sub.2 O.sub.2.
U.S. Pat. No. 4,959,113 discloses a method of using an aqueous abrasive composition for polishing metal surfaces. The aqueous abrasive composition comprises water, an abrasive, e.g. CeO.sub.2, Al.sub.2 O.sub.3,ZrO.sub.2, TiO.sub.2, SiO.sub.2, SiC, SnO.sub.2, or TiC, and a salt including a metal cation of Group IIA, IIIA, IVA or IVB and an anion of chloride, bromide, iodide, nitrate, sulfate, phosphate or perchlorate. This patent also discloses the use of hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid to adjust the pH of the abrasive composition to be in the range of 1 to 6.
U.S. Pat. No. 5,391,258 discloses an abrasive composition for polishing silicon, silica or silicate composite. The abrasive composition comprises, in addition to abrasive particles, hydrogen peroxide and potassium hydrogen phthalate.
U.S. Pat. No. 5,114,437 discloses a polishing composition for an aluminum substrate comprising an alumina polishing agent having an average particle size of 0.2 to 5 .mu.m, and a polishing accelerator selected from the group consisting of chromium(III) nitrate, lanthanum nitrate, ammonium cerium(III) nitrate, and neodymium nitrate.
U.S. Pat. No. 5,084,071 discloses a chemical mechanical polishing slurry for an electronic component substrate. The polishing slurry comprises no more than I weight percent of alumina, abrasive particles (e.g. SiO.sub.2, CeO.sub.2, SiC, Si.sub.3 N.sub.4, or Fe.sub.2 O.sub.3 particles), a transition metal chelated salt (e.g. ammonium iron EDTA) for use as a polishing accelerator, and a solvent for said salt.
U.S. Pat. No. 5,336,542 discloses a polishing composition comprising alumina abrasive particles and a chelating agent selected from the group consisting of polyaminocarboxylic acid (e.g. EDTA) and sodium and potassium salts thereof. The composition may further comprise beohmit or an aluminum salt.
U.S. Pat. No. 5,340,370 discloses a chemical mechanical polishing slurry for tungsten or tungsten nitride film, which comprises an oxidizing agent such as potassium ferricyanide, an abrasive, and water, and has a pH between 2 and 4.
U.S. Pat. No. 5,516,346 discloses a slurry for chemical mechanically polishing a titanium film, said slurry comprising potassium fluoride in a concentration sufficient to complex said titanium film and an abrasive such as silica, and having a pH less than eight
WO 96/16436 discloses a chemical mechanical polishing slurry which comprises abrasive particles having a median particle diameter less than 0.400 microns, a ferric salt oxidant, and an aqueous surfactant suspension of a mixture of propyleneglycol and methylparaben.
The salts generally used to accelerate the abrasion rate include ferric ions (such as Fe(NO.sub.3) and K.sub.3 Fe(CN).sub.6) or potassium ions (such as KIO.sub.3). However, these metal ions would contaminate wafers and CMP device so as to necessitate subsequent cleaning steps and to reduce shelf life of the CMP device. In addition, potassium ions are so mobile that they will penetrate dielectric layers so as to reduce the reliability of IC.
In the process for producing integrated circuits, Ta or TaN film is most commonly used to enhance the adhesion of copper to a silica insulator layer. Moreover, Ta or TaN film is also commonly used as a barrier metal film. In theory, Ta or TaN should be polished in a rate close to that of copper. Nevertheless, since Ta has a high chemical resistance and is hard to be oxided, effective polishing of Ta is usually difficult to be achieved in the process for producing copper circuits. Furthermore, since the barrier film is hard to be removed by polishing, this normally causes depressions on copper circuits.
Accordingly, in semiconductor processing, need still exists for abrasive compositions which are more economical, have high polishing performance, and are able to reduce depressions on metal circuits.